Effect Of Agrochemical Application On Soil Nematode Diversity In The Reclamation Progress Of Sanjiang Plain

Based on a field investigation of the structure and diversity of thesoil nematode community in different ages of reclamated farmlands, thispaper focus on the effect of agrochemical and reclamation on the soilnematode community, and the effect of three non-target agrochemicals onthe soil nematode community. This paper included one investigation andtwo field control experiments. The investigation was taken on thenematode community structure of original wetlands and soybeanfarmlands which were reclaimed from original wetlands in early21stcentury, the mid90’s and the early80’s respectively. From theinvestigation, we revealed the characteristic of soil nematode communityin different ages of reclamated farmlands. In the field control experiment,we researched on the effect of reclamation and agrochemical on the soilnematode community, and the effect of three different non-targetagrochemicals on the soil nematode community. Our results showed that:1. Wetland reclamation had a strong effect on the soil nematodecommunity. Short-term agricultural cultivation increased the density andspecies richness of nematode, enhanced the diversity of soil nematode.However, the long-term agricultural cultivation reduced the density and species richness of soil nematodes. The agrochemical had positive effecton the soil nematode community in the short-term, but the soil nematodecommunity showed a distinct trend of recover.2. Different non-target agrochemicals had different effects on thesoil nematode community. The effect of blended agrochemicals wasstronger than single agrochemical, and continuous application wasstronger than one-time application in density and species richness.3. Both the reclamation and agrochemicals application reduced therelative abundance of plant-parasites, and increased the relativeabundance of bacterivores. The rising of nematode channel ratio (NCR)means accelerated decomposition rate of soil organic matter. The PPI/MIindex could sensitively reflect the disturbances of soil environment.Based on the results of our experiment and on the aim of soilbiodiversity protection, we propose the following suggestions:intensifying the protection of the rest wetlands and strictly prohibitreclamation; promoting the green agriculture and cutting down theapplication of agrochemicals; reducing the frequency of agrochemicalapplication in existing farmlands and establishing the system of rotation,protecting the repair and recovery process of soil ecosystem.